[docs] [lit] Add a more helpful description for lit.py's -s flag.

Reviewed By: yln

Differential Revision: https://reviews.llvm.org/D82808

llvm/docs/CommandGuide/lit.rst

@@ -81,6 +81,7 @@ OUTPUT OPTIONS
 .. option:: -s, --succinct
 
  Show less output, for example don't show information on tests that pass.
+ Also show a progress bar, unless ``--no-progress-bar`` is specificed.
 
 .. option:: -v, --verbose
 

llvm/utils/lit/lit/cl_arguments.py

@@ -42,7 +42,9 @@ def parse_args():
             help="Suppress no error output",
             action="store_true")
     format_group.add_argument("-s", "--succinct",
-            help="Reduce amount of output",
+            help="Reduce amount of output."
+                 " Additionally, show a progress bar,"
+                 " unless --no-progress-bar is specified.",
             action="store_true")
     format_group.add_argument("-v", "--verbose",
             dest="showOutput",